Fabio Carli

This study presents the multi‐disciplinary approach used to study a quad‐band dichroic mirror to be installed in the European Space Agency deep space antennas. Traditional electromagnetic (EM) analyses based on a uniform plane wave incidence were augmented by advanced numerical techniques to investigate the impact of the dichroic mirror on the overall antenna performance. In addition, along with the EM design, a parallel study considering mechanical, thermal and power‐handling aspects allowed their impact on the EM behaviour of the dichroic mirror to be evaluated. This comprehensive study permitted an optimum design to be achieved for the dichroic mirror, which accounts for the actual operational conditions of the mirror itself when installed in the antenna. The device was manufactured and measured, verifying also the mechanical and thermal theoretical predictions, obtaining an excellent agreement between simulations and experimental results.

This paper presents the multi-disciplinary approach used to study a quad-band frequency selective surface to be installed in the European Space Agency deep space antennas. The electromagnetic design is augmented by the reciprocal interaction with mechanical, thermal and power handling analyses that allow a comprehensive study able to meet the severe specifications required to this frequency selective surface. The device is manufactured and tested and an excellent agreement is achieved.

Commonly used perioperative measurements of hemodynamics, such as Swan-Ganz catheter assessment, are invasive and may not be reliable under pneumoperitoneum. The purpose of this study was to validate the use of esophageal Doppler for noninvasive hemodynamic monitoring under pneumoperitoneum in an experimental pig model.

Background:  The aim of this study was to investigate the effect of general anaesthesia combined with remifentanil or epidural blockade on glucose metabolism during surgery.Methods:  We randomly assigned patients undergoing elective colorectal surgery to receive either desflurane anaesthesia supplemented with intravenous remifentanil (n = 7) or desflurane anaesthesia supplemented with epidural bupivacaine (n = 7). Plasma concentrations of glucose, lactate, free fatty acids (FFA), insulin, glucagon and cortisol were measured before and after 2 h of surgery. Pre‐ and intraoperative whole body glucose production and glucose clearance, an indicator of glucose uptake, were determined by an isotope dilution technique using [6,6–²H₂]glucose.Results:  In both groups intraoperative glucose production ( P< 0.05) and uptake ( P< 0.05) decreased. Plasma glucose concentrations ( P< 0.05) increased during surgery but did not exceed the normal range (remifentanil group: 5.7 ± 0.7 mmol l⁻¹, epidural group: 5.8 ± 0.4 mmol l⁻¹). The plasma concentrations of lactate, FFA, insulin and glucagon remained unchanged during the operation. The plasma cortisol concentration in both groups increased intraoperatively (P< 0.05).Conclusion:  Both desflurane/remifentanil and desflurane/epidural anaesthesia decrease the intraoperative rate of whole body glucose production, thereby attenuating the hyperglycaemic response to colorectal surgery.

The main object of the paper is the implementation of two different approaches for the estimation of the modulus of elasticity and of the failure strain/stress in micro machined structures manufactured of epitaxial polycrystalline silicon (15 μm thick film). The micro-test-structures are produced using a standard THELMA process becoming an integral part of a MEMS actuator of comb-finger type. The micro-motor is designed to develop electrostatic in plane forces of desired intensity when fed by suitable electric potential difference.

Increasing diffusion and complexity of mitral valve repair procedures may prompt an interest in the evaluation of the patterns of stress distribution on the chords, which are, from the structural mechanical point of view, the weakest element of valve apparatus. This theoretical analysis concentrates in particular on the mitral valve anterior leaflet. As is known, the vast majority of the chordae are attached to the anterior leaflet within the coaptation area; during systole they are then necessarily parallel, aligned along the same plane as that of the leaflets' coaptation surface, to which they are attached; moreover the thickness of the chordae increases significantly from the marginal chordae to the more central ones. In normal conditions during systole the progressively wider coaptation surface causes the increasing stress to be supported by an increasing number of progressively thicker chords, which are substantially parallel and aligned on the coaptation surface plane in such a way that they can share the stress between them, according to their thickness; in other words chords form a multifilament functional unit which enrolls elements of increasing thickness in response to the mounting stress. The geometrical modifications of the valve apparatus architecture (annulus dilatation, leaflet retraction, chordal elongation or retraction) often associated with valve insufficiency due to chordal rupture, have the common result of causing, during systole, a radial disarrangement of the direction of most of the secondary chordae which are no longer parallel, aligned on the coaptation surface plane. Due to the negligible elastic module of the valve leaflet, in this new arrangement the various chordae cannot share the stress between themselves as they do in a normal physiological situation; on the contrary the thinner chordae nearer to the free margin are also loaded with the peak systolic stress, thus generating conditions favoring their rupture. It can, therefore, be hypothesized that the anatomopathological picture of valve insufficiency due to chordal rupture may be the final event of a series of geometrical modifications of valve apparatus architecture, the common consequence of which is to load thinner marginal chords with peak systolic stress from which they are normally spared, thus favoring their rupture.